I only “immediately” use guides for RPGs because I hate missing out stuff (sub quests, hidden items, etc.) and wouldn’t like spending hundreds of hours replaying them just for such reasons. For SIMs (as rare as they get nowadays), I usually try a first time without a guide “to get a feeling of the game” before I read one to check the required parameters to open a route. For AVGs which routes are obviously determined by your choices (e.g. with the icons of the girl to whom a choice applies attached to said choice), a guide isn’t really necessary so I go without for the characters I like, enjoying the story, and may use one to browse over the characters I don’t like. For AVGs which routes aren’t obviously determined by your choices, I always try a first time making choices “as I would if I were the main protagonist” to see with which girl I’m most compatible then try to get the other routes without a guide. I’d only use them when not being able to get one, or because I don’t think the remaining girls/routes would interest me.
All in all, I don’t often use a guide because I hate most knowing in which route I actually am, making it a challenge to get a route. I guess I could use them in order to speed my playing time, but time is rarely a consideration to me (which may explain why I’d need decades in order to complete my backlog~)
At the contrary, I personally think most modern erogames are very easy to complete, with very few choices overall, and most pertinent to a route. Games of yore, where you had to talk to everyone, click everywhere, do every possible action, or where you had countless choices among which only a handful actually had an incidence on the “story”, were infinitely harder.